1. Field of the Invention
The invention relates to a sequential direction indicator, and more particularly, to a direction indicator wherein lamp sets forming adjacent arrowheads or opposed arrowheads joined by a set of lamps forming a shaft are sequentially actuated in synchronism and wherein the illumination value of the lamps may be adjusted to any desired level.
2. History of the Prior Art
Different circumstances such as highway construction and repair make it desirable to be able to convey a warning for drivers of motor vehicles to change direction or lane. Warning should be instantly recognizable and attract the attention of the observer at first glance. Direction indicators such as reflectorized signs, which are illuminated by headlights of an approaching auto, and even signs which are formed of steadily light sources are insufficient to attract the attention of a motorist travelling at high speed. It is not uncommon for a turnpike motorist to undergo driving hypnosis and be in a semiconscious state at the time a direction warning is given. This requires a driver to be startled into consciousness by the warning sign.
To overcome the problems involved, arrays of flashing lamps and sequentially energized signs heretofore have been developed. In some such systems, a lamp set forming an arrowhead is continuously illuminated and a set of lamps forming an arrow shaft is sequentially energized to indicate the desired direction. An example of this type of system is that disclosed and claimed in U.S. Pat. No. 3,479,641 to Gerald C. Summers. While such systems are adequate for certain applications, in other situations it is desired to provide features which are not incorporated therein. For example, it is sometimes desirable to control the sequential energization of a lamp set with a master clock so that the rate of sequencing can be varied to conform with various state governmental requirements. Prior art systems, which use a series of relaxation oscillators to control sequencing, cannot be varied in rate without disturbing the symmetry of the sequencing. In certain situations, it is desirable to be able to dim the lamps of warning array to a very low level of illumination to avoid the risk of blinding motorists. Prior art sequence controls have not permitted dimming of sequenced lamps to much less than 2/3 of their total brightness because they were unable to dissipate the heat generated by dimming.